Electric field meters of this kind are believed to be used as thunderstorm warning devices. The document DE 1 591 932, for example, discusses a diaphragm-less field mill for measuring electrostatic fields and voltages; in the field mills according to the existing art, a vane wheel driven by a motor and connected via wiper contacts to ground is disposed between a perforated shield functioning as a diaphragm, and a high-resistance collector electrode held in the form of a circular disk in the insulating ring, in such a way that a periodically fluctuating portion of an external electrostatic force field arrives at the collector electrodes and influences an alternating electrical charge there.
Measuring instruments for measuring the electric field, in particular electric field meters (also referred to as e-field meters), whose manner of operation is based on the known principle of the field mill, are already known in the existing art. Measuring instruments of this kind are relatively large in comparison with micromechanical structures, for example several centimeters in at least one spatial dimension. In addition, large electric field meters of this kind are dependent on a relatively strong energy source. These electric field meters are used, for example, as thunderstorm warning devices, being configured to measure the static electric field of the near-surface atmosphere. Provision is made here that when the electric field strength exceeds a specific limit value, for example 1 kV/m, a thunderstorm warning display is activated even before the first lightning bolt. Electric field meters configured as thunderstorm warning devices make use of the knowledge that a rise in the electric field strength of the near-surface atmosphere to values greater than 1 kV/m, or a change in the polarity of the electric field, indicates an approaching thunderstorm front. Such electric field meters are used, for example, for thunderstorm warning at high-altitude observatories, the voltage values being recorded.
Also known are thunderstorm warning devices configured as lightning detectors, which measure the pulsed alternating electric field of the electromagnetic lightning pulses caused by lightning, which are also referred to as LEMP or “sferics.” Lightning detectors have a receiver for alternating electromagnetic fields, and are provided for the detection of pulses at various frequencies. Lightning detectors detect the lightning bolts of approaching thunderstorms, for example, over comparatively long distances.
Thunderstorms can be life-threatening, especially for a person who is outdoors. In good weather the electric field strength is in the range from approx. 100 V/m to 300 V/m. Below a thunderstorm the electric field strength has values of up to −30,000 V/m or +30,000 V/m. These changes in the electric field occur earlier in time than a thunderstorm, and can be used to predict the thunderstorm. Changes in the field strength of the atmosphere's electric field can be used as thunderstorm indicators and/or lightning indicators. The thunderstorm warning devices according to the existing art are, however, cumbersome, large, and dependent on an energy source that the user must also carry. An object of the present invention is therefore to make available a thunderstorm warning device, for incorporation into small portable devices for use outdoors or in vehicles, that does not exhibit the disadvantages of the existing art and that is particularly light and portable in use. This makes possible field strength measurement, for example during a thunderstorm, that is particularly simple and energy-saving, in particular cost-saving, compared with the existing art.